There are 2 recognized subspecies, one in the Baltic sea and the other in North west and east of the Atlantic (this is the other common species found in UK waters.
There are a number of well known breeding colonies around the coast of the UK. Notable colonies in the UK, include Blakeny point in Norfolk, the Farne and Orkney islands. There is also colonies around the USA and Canada.
Around much of the world, the primary hunter is the Orca, though there are also a variety of sharks that will also take one if given the chance. Recent observations have also shown that they take harbour seals and porpoises if they get the chance.
There has also been a significant level of cannibalism where male seals kill pups of its own species.